The present disclosure relates generally to power generation systems and, more specifically, to systems and methods of controlling an overspeed event in a gas turbine engine.
At least some known gas turbine engines include at least one compressor, a combustor, and a high-pressure turbine coupled together in a serial flow relationship. More specifically, the compressor and high-pressure turbine are coupled through a shaft to form a high-pressure rotor assembly. Air entering the turbine engine is mixed with fuel and ignited to form a high energy gas stream. The high energy gas stream flows through the high-pressure turbine to rotatably drive the high-pressure turbine such that the shaft rotatably drives the compressor. After being discharged from the high-pressure turbine, the gas stream continues to expand as it flows through a low-pressure turbine positioned aft of the high-pressure turbine. The low-pressure turbine includes a rotor assembly coupled to a drive shaft and a fan. The low-pressure turbine rotatably drives the fan through the drive shaft. In some embodiments, the gas stream discharged from the turbines is channeled through a heat recovery steam generator. As such, hot steam is produced, and the steam is channeled through a steam turbine assembly for further producing power.
At least some known gas turbine engines may be susceptible to damage as a result of an overspeed event. For example, an overspeed event may occur when a generator coupled to the gas turbine engine is uncoupled from an external electrical load. The sudden loss of load on the generator can cause the speed of the gas turbine engine to dramatically increase. At least some known gas turbine engines include systems for shutting down the gas turbine engine upon detection of an overspeed even, such as a fuel shutoff valve that cuts off the flow of fuel supplied to the combustor. While the fuel shutoff valve is effective at shutting down the gas turbine engine, it is generally desirable to further reduce the amount of time that the gas turbine engine operates at an overspeed condition.